package org.kgduyjj.toolkit.util;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;

import org.kgduyjj.toolkit.exception.AlgorithmsException;


/**
 * MD5加密工具类
 * 
 * @author Kgduyjj
 * @since 2020-07-26
 * @version 1.0.0-Alpha
 *
 */
public final class MD5Utils {
	private static final String EMPTY = "";
	/**
	 * 默认的密码字符串组合，用来将字节转换成 16 进制表示的字符,Apache校验下载的文件的正确性用的就是默认的这个组合
	 */
	protected static final char HEX_DIGITS[] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd',
			'e', 'f' };
	protected static MessageDigest messageDigest = null;
	protected static final int SHORT_DIGIT_START = 8, SHORT_DIGIT_END = 24;
	static {
		try {
			messageDigest = MessageDigest.getInstance("MD5");
		} catch (NoSuchAlgorithmException e) {
			e.printStackTrace();
		}
	}

	/**
	 * 获取文件MD5值
	 * 
	 * @param file
	 * @return
	 * @throws IOException
	 */
	public static String md5File(File file) throws IOException {
		InputStream fis;
		fis = new FileInputStream(file);
		byte[] buffer = new byte[1024];
		int numRead = 0;
		while ((numRead = fis.read(buffer)) > 0) {
			messageDigest.update(buffer, 0, numRead);
		}
		fis.close();
		return bufferToHex(messageDigest.digest());
	}

	/**
	 * MD5加密文字的算法核心，不公开
	 * 
	 * @param text
	 * @return
	 */
	private static String _md5(String source) {
		if ((source == null) || (source.length() == 0)) {
			return EMPTY;
		}
		byte[] buffer = source.getBytes();
		messageDigest.update(buffer);
		return bufferToHex(messageDigest.digest());
	}

	/**
	 * 密码字符串MD5加密 32位小写
	 * 
	 * @param str
	 * @return
	 */
	public static String md5(String source) {
		return _md5(source).toLowerCase();
	}

	/**
	 * 密码字符串MD5加密 32位大写
	 * 
	 * @param str
	 * @return
	 */
	public static String MD5(String source) {
		return _md5(source).toUpperCase();
	}

	/**
	 * 密码字符串MD5加密 32位大写，处理多条并行文本
	 * 
	 * @param multiText
	 * @return
	 */
	public static String MD5(String... multiSource) {
		if ((multiSource == null) || (multiSource.length == 0)) {
			return EMPTY;
		}
		StringBuilder builder = new StringBuilder();
		for (String source : multiSource) {
			builder.append(MD5(source));
		}
		return MD5(builder.toString());
	}

	/**
	 * 密码字符串MD5加密 16位小写
	 * 
	 * @param source
	 * @return
	 */
	public static String md5X16(String source) {
		String md5X32 = md5(source);
		return (md5X32 == null || md5X32.length() == 0) ? md5X32 : md5X32.substring(SHORT_DIGIT_START, SHORT_DIGIT_END);
	}

	/**
	 * 密码字符串MD5加密 16位大写
	 * 
	 * @param source
	 * @return
	 */
	public static String MD5X16(String source) {
		String md5X32 = MD5(source);
		return (md5X32 == null || md5X32.length() == 0) ? md5X32 : md5X32.substring(SHORT_DIGIT_START, SHORT_DIGIT_END);
	}

	private static String bufferToHex(byte bytes[]) {
		return bufferToHex(bytes, 0, bytes.length);
	}

	private static String bufferToHex(byte bytes[], int m, int n) {
		StringBuffer stringbuffer = new StringBuffer(2 * n);
		int k = m + n;
		for (int l = m; l < k; l++) {
			appendHexPair(bytes[l], stringbuffer);
		}
		return stringbuffer.toString();
	}

	private static void appendHexPair(byte bt, StringBuffer stringbuffer) {
		char c0 = HEX_DIGITS[(bt & 0xf0) >> 4];// 取字节中高 4 位的数字转换， 为逻辑右移，将符号位一起右移,此处未发现两种符号有何不同
		char c1 = HEX_DIGITS[bt & 0xf];// 取字节中低 4 位的数字转换
		stringbuffer.append(c0);
		stringbuffer.append(c1);
	}

	private static final String toHex(byte hash[]) {
		if (hash == null) {
			return null;
		}
		StringBuffer buf = new StringBuffer(hash.length * 2);
		int i;
		for (i = 0; i < hash.length; i++) {
			if ((hash[i] & 0xff) < 0x10) {
				buf.append("0");
			}
			buf.append(Long.toString(hash[i] & 0xff, 16));
		}
		return buf.toString();
	}

	/**
	 * 
	 * @param s
	 * @return
	 */
	public static String hash(String source) {
		try {
			return new String(toHex(_md5(source).getBytes("UTF-8")).getBytes("UTF-8"), "UTF-8");
		} catch (Exception e) {
			throw new AlgorithmsException("MD5处理hash失败");
		}
	}
}
